This invention relates to tool components.
Tool components, particularly cutting elements, in the form of composite abrasive compacts are well known in the art and used extensively in various cutting, drilling, milling and other abrasive operations. The tool components generally comprise a layer or table of ultra-hard abrasive material bonded to a cemented carbide substrate. The tool component has a generally cylindrical shape with the layer or table of ultra-hard abrasive material being bonded to one of two flat ends of a cylindrical substrate. The ultra-hard abrasive material is generally polycrystalline diamond (PCD) or polycrystalline cubic boron nitride (PCBN).
In use, the upper exposed peripheral edge of the layer or table of ultra-hard abrasive material is the edge which provides the cutting edge for the component. In drilling, for example, the cutting element is generally mounted at a negative rake angle relative to the direction of advancement of the component through the rock, as illustrated by FIG. 1 of the attached drawings. Referring to FIG. 1, the prior art cutting element comprises a layer 10 of ultra-hard abrasive material bonded to a cemented carbide substrate 12. The cutting element has a cylindrical shape. The peripheral edge 14 of the layer 10 provides the cutting edge for the element. FIG. 1 illustrates the cutting element advancing in the direction of arrow 16 into a rock face or other workpiece 18. In so advancing, a considerable load is placed on the front flat face 20 of the layer 10. This in turn creates a significant bending moment on the cutting element and hence stress on this element. This stress leads to fracture and spalling. U.S. Pat. No. 4,109,737 discloses a rotary drill bit for rock drilling which comprises a plurality of cutting elements mounted in a crown of the drill bit. Each cutting element comprises an elongate pin with a thin layer of crystalline diamond bonded to the free end of the pin. The layer of polycrystalline diamond presents a curved cutting surface for the drill bit.